As known in the mechanical arts, there are myriad situations in which it is desirable to control the motion of a movable part. By way of non-limiting example, such control is desirable in the context of internal combustion engines. FIG. 1 illustrates a typical scenario, specifically a valve seating control device 100 used to control motion of at least one engine valve 110 (only a single valve shown for ease of illustration), any of which may comprise an exhaust valve, an intake valve or an auxiliary valve. The device 100 may include one or more valve train elements 120 operatively connected to a motion generating source 130, a valve seating device 140 and the at least one engine valve 110. The motion generating source 130 may optionally comprise a lost motion system. As known in the art, the valve train elements 120 may transmit a valve actuation motion to the engine valve 110, for example, to produce various engine valve events, such as, but not limited to, main intake, main exhaust, compression release braking, bleeder braking, exhaust gas recirculation, early exhaust valve opening and/or closing, early intake opening and/or closing, centered lift, etc.
The motion generating source 130 may comprise any known combination of elements for imparting a linear actuation motion, particularly in the context of internal combustion engines. For example, the motion generating source 130 may comprise a camshaft having one or more rotating cams. Alternatively, the motion generating source 130 may receive motion from another engine component and transfer the motion as an input to the lost motion system, for example, or directly to the valve train elements 120. As known in the art, a lost motion system may comprise any structure that connects a source of motion to the valve train elements 120 and that is capable of selectively losing part or all of the motion imparted to it.
The engine valve 110 may be disposed within a sleeve or housing 111, which in turn is provided in a cylinder head 112. The engine valve 110 may be adapted to slide up and down relative to the sleeve 111 and may be biased into a closed position by a valve spring 113. The valve spring 113 may be compressed between the cylinder head 112 and a valve spring retainer 114 that may be attached to a valve stem, thereby biasing the engine valve 110 into an engine valve seat 116. When the engine valve 110 is in contact with the engine valve seat 116, the engine valve 110 is effectively in a closed position.
The valve train elements 120 may receive a force from the motion generating source 130 (e.g., via a lost motion system or directly from the source of motion) and may transfer this force to the engine valve 110. The valve train elements 120 may also transmit the force of the valve spring 113 that biases the engine valve 110 into a closed position back to the lost motion system, if present, and/or the valve seating device 140, although this is not a requirement as the force of the valve spring 113 may be more directly transmitted, e.g., via a valve stem or the like. As shown, the valve seating device 140 may be operatively connected to the valve train elements 120. When the valve seating device 140 is activated, it may provide a resistance to the bias of the engine valve spring 113 through the valve train elements 120. Alternatively, the valve seating device 140 may be deployed within a lost motion system, with the force of the valve spring 113 transmitted back accordingly.
For example, when a lost motion system acts to lose the motion of the motion generating source 130, the engine valve 110 normally may close in “free-fall,” a state in which the engine valve 110 may contact the engine valve seat 116 at an undesirably high rate of speed. That is, the high seating velocity of the valve may lead to excessive noise, vibration and harshness, particularly at lower engine speeds, as well as valve damage. In order to slow the velocity at which the engine valve 110 closes when, in this case, the lost motion system is losing motion, the valve seating device 140 may be used. That is, the valve seating device 140 may provide control over the engine valve 110 as it comes into contact with the engine valve seat 116. As known in the art, the valve seating device 140 may slow the speed at which the engine valve 110 contacts the engine valve seat 116 by opposing the motion of the engine valve 110 through the valve train elements 120, or components of the lost motion system if the valve seating device 140 is deployed therein. Those having ordinary skill in the art will appreciate that other scenarios in which it is desirable to use the valve seating device 140 in the absence of operation of the lost motion system 130 are known.
An example of a valve seating device 140 is schematically illustrated in FIG. 2 in which an engine valve 210 (or component of a valve train or lost motion system) interacts with a first chamber 220. Prior to a valve seating event (such as during the valve opening period), a volume of fluid (such as engine oil) is forced in a first chamber 220. As shown, the first chamber 220 communicates with a second chamber 240 via an orifice 230. As used herein, reference to an “orifice” encompasses a single orifice or a plurality of orifices operating in conjunction. Although not illustrated in FIG. 2, the second chamber 240 typically vents to a low pressure drain or the like. During the valve seating event, pressure is generated in the first chamber 220 due to interaction of the valve 210 with the fluid in the first chamber 220, typically via an intervening slave piston or the like. The size and shape of the orifice 230 results in different valve seating velocity of the valve 210 as the flow coefficient and the flow area of the orifice define the flow rate of the fluid out of the first chamber 220 through the orifice 230 and into the second chamber 240. In known embodiments, the size and shape of the orifice 230 is adjustable, thereby permitting greater control of the fluid flow between chambers 220, 240 and, consequently, the seating velocity of the engine valve 210. Specifically, a feature of prior art valve seating devices 140 is that they are dependent upon position of the engine valve when adjusting the velocity of the engine valve. That is, control of the size and shape of the orifice 230 is dependent upon the position of the valve 210 resulting in constant seating velocities regardless of other engine-related parameters. In some situations, however, such uniform operation regardless of context could be problematic because the constant seating velocity of an engine valve can interfere with overall engine operation.
Thus, it would be advantageous to provide control over movable parts that is responsive to a broader array of conditions.